So... my Ikea couch is currently covered in this: (it's sort of a light chartreuse)

And, I want to dye it a dark chocolate brown. It's 63% cotton and 37% linen. Is this even possible? If I do it myself at home, is there a way to ensure that the color comes out even and not tie-dyed looking? What products would you recommend?

Or... Are there places that do this professionally? I thought maybe cleaners or upholsterers, but I can't find any that advertise dyeing.

Thats gonna be really hard to dye. I would say get color remover and remove all the color first. Bleach didnt work on ours. Ours was a deep burgendry and we tried to go black. 6 boxes of dye and two bottles of bleach latter we quit.

i dyed my klippan cover, however mine was already a unbleached natural color. so i would definitely recommend a color remover first, and i would do it in the washing machine. i don't know if i would recommend a choc. brown color though, b/c that is what i tried, and i could never get it to look brown, the color was even , but always looked more purple than anything, after 3 times though i just gave up and settled for a funky purple/brown.the funny thing is, I'm buying another klippan cover so i can dye it that green color that your cover is, go figure.